This invention relates to an auxiliary front wheel drive system for a vehicle, and more particularly, to such a system which utilizes implement system pressurized fluid flow for driving said front wheels.
Systems of the general type disclosed herein are shown in U.S. Pat. No. 3,458,005 to Malm et al., U.S. Pat. No. 3,480,099 to Nighswonger et al., and U.S. Pat. No. 3,481,419 to Kress et al. In such systems, a vehicle includes motors for driving the front wheel thereof, such motors being of the hydraulic type to be driven by fluid under pressure, in a series or parallel mode. Pressurized fluid supplied to each motor actuates a clutch associated with that motor so that a front wheel of the vehicle is drivingly engaged with the motor.
In any of the clutch engaging systems of these patents, it will be seen that the fluid pressure to be applied to such clutch for engagement thereof may be directed from either the fluid conduit of the motor associated with such clutch, or the fluid outlet conduit of such motor. While it will be seen that, in such situations, the higher of such two fluid pressures may be applied to the clutch for the engagement thereof, such clutch may in other situations be exposed to both the higher and lower pressures defined by such motor inlet and outlet conduits, resulting in a less than maximum fluid pressure being applied to such clutch to actuate it.
In addition, in the area of such clutch in any of these three patents, no means are provided for preventing excessive pressure buildup in the clutch.
Of more general interest in this area are U.S. Pat. No. 2,818,699 to Clemson, U.S. Pat. No. 3,153,908 to Lawrence, U.S. Pat. No. 3,184,994 to Stahl, U.S. Pat. No. 3,186,506 to Leach, U.S. Pat. No. 3,255,840 to Tangen, U.S. Pat. No. 3,272,576 to Budzich, U.S. Pat. No. 3,272,279 to Budzich, U.S. Pat. No. 3,302,741 to Brazuk, U.S. Pat. No. 3,354,977 to Swift, U.S. Pat. No. 3,391,753 to Anderson, U.S. Pat. No. 3,361,223 to Baver, U.S. Pat. No. 3,415,334 to Vriend, U.S. Pat. No. 3,469,648 to Cannon, U.S. Pat. No. 3,447,547 to Kress et al., U.S. Pat. No. 3,493,067 to Rumsey, U.S. Pat. No. 3,522,861 to Middlesworth et al., and U.S. Pat. No. 3,579,988 to Firth et al.